[System package] System package should indicate that it required root privilages to read system.log file

[nimarezainia]

When the Elastic Agent is installed in an unprivileged mode, it will not have the requisite permissions to read system logs as they require higher privileges:

-rw-r-----@  1 root            admin     13967 May  6 11:32 system.log
-rw-r-----   1 root            admin       895 May  5 00:00 system.log.0.gz
-rw-r-----   1 root            admin       950 May  4 00:11 system.log.1.gz
-rw-r-----   1 root            admin       978 May  3 00:03 system.log.2.gz
-rw-r-----   1 root            admin       953 May  2 00:15 system.log.3.gz
-rw-r-----   1 root            admin       942 May  1 00:04 system.log.4.gz
-rw-r-----   1 root            admin       961 Apr 30 00:02 system.log.5.gz

Package developers do have the ability to nominate their package OR datastream to require root privileges.

Request
For the system package to indicate that logs-system.syslog requires root privilege.

cc: @cmacknz @kpollich